In addition to the conventional telephony service features, modern forms of communication such as “Instant Messaging” and “Presence” are becoming increasingly important. In particular, the younger generation is already used to working with these forms of communication today, and it is to be assumed that they will also want to use these forms of communication in the working environment. This is supported by some firms, for example, which are moving toward this environment by using the IP convergence products.
In telecommunication systems, one subscriber learns of the absence of another as a result of the fact that the other subscriber does not accept the connection when a connection setup is attempted and, if an absence text has been defined, as a result of the fact that the calling subscriber receives this text message. If the called subscriber is already having a conversation at that time, this is signaled to the caller by means of the busy tone.
However, the caller only receives this information if said caller calls, i.e. dials the called party. The purpose of a “presence service” is to provide a subscriber with absence information or information about the availability of other subscribers directly, without the need to actually contact these other subscribers. This information can be, for example: Present, Away on vacation, Do not disturb, At lunch, etc.
Such presence services already exist for the internet data medium. The information is displayed to the subscriber in a subscriber list, i.e. a so-called buddy list. These buddy lists are a personal list of one or more personally selected subscribers whose presence status one wishes to track. In particular, they provide information about whether a selected person is currently “online”, i.e. available.
Status information for every subscriber is already stored in many telecommunication systems or PBX systems today using the absence text and station guarding service features. This information is currently provided to the terminals when a call is made.
For example, a subscriber can have activated the standard absence text “Away on vacation until June. 20”.
If a call to this subscriber is then made by another subscriber who is connected to the same telecommunication system, the text message is sent to the calling subscriber and displayed in the display of the caller.